Longline fishing is a commercial fishing method used mainly for tuna fishing in the South Pacific. Fishing vessels are large ocean-going fishing vessels. Release a mainline (120 ~ 150Km) from the ship into the sea, tie a certain number of branch lines and floats to the mainline at a certain distance, use the buoyancy of the float to suspend the branch line in a certain depth of water, and lure it with fishing lures (or pseudo-baits) Fish are hooked to achieve the purpose of fishing. The fishing boat technology is most developed in Japan, followed by South Korea and Taiwan Province of China. Longline fishing is one of the main fishing methods for large migratory fish. Tuna, swordfish, swordfish, etc. are its main fishing targets.